soc: intel_adsp/ace: use custom arch_spin_relax()

Intel Audio DSP ACE needs to use arch_spin_relax() to give
the bus more time to propagate the RCW transactions among
CPUs, and to avoid sending too many requests to the bus
after failing to lock spinlocks. However, the number of
NOPs results in a very big arch_spin_relax() that spans
multiple instruction cache lines, and requires evicting
them just for NOPs.  With 5 CPUs, it can span 6 cache
lines (if using nop.n instead of nop). That's a waste of
space and cache. So instead, we do a tight loop instead.
Since the SoC supports zero-overhead loops, this should
have minimal performance impact.

Signed-off-by: Daniel Leung <daniel.leung@intel.com>